It is known to mount an air blower unit at the outlet of an air admission housing for supplying the blower with air from outside the vehicle and/or with recycled air. The air blower commonly has a casing in the form of a volute, which is provided with an air inlet orifice-and an air outlet or delivery orifice, and which contains a motorized blower, that is to say an assembly of a motor with a blower rotor for drawing a stream of air through the inlet orifice and for delivering it through the delivery orifice. Having regard to the configuration of the volute, the stream of air under pressure passes through the delivery orifice in a direction which is generally at right angles to the direction in which the air stream is passed through the inlet orifice.
The delivery orifice is commonly connected to the air inlet of a distribution housing which is arranged to distribute the stream of pressurised air into the cabin of the vehicle after it has been heated if required and possibly cooled if the installation is adapted for air conditioning.
In some types of vehicle in which the volume of the cabin is large, it may be necessary to provide two air blowers, the respective delivery orifices of which are connected to the two ends of a common distribution housing. One installation of this type is described in the specification of French patent application No. 90 05680 filed on 4 May 1990.
Generally the distribution housing is arranged transversely below the windshield of the vehicle, and the two air blower units are arranged respectively on the left hand side and the right hand side of the vehicle, in such a way that their delivery orifices are connected to the distribution housing at different levels. Therefore, in any given installation, it is normally necessary to provide two air blower units having different configurations, so that it is possible to dispose their respective delivery orifices with respect to the distribution housing in opposed relationship to each other.
In addition, according to the amount of space available below the fascia, it may be desirable, for two different versions of a particular vehicle, to provide in one version that the delivery orifice of the left hand air blower unit shall be at a higher level than the delivery orifice of the right hand air blower unit, or vice versa. This is typically the case in vehicles that are designed to be built in both left hand drive and right hand drive versions.
It is thus necessary to be able to provide four different configurations of air blower unit, which proliferates the number of components that have to be provided.